I call it "irská píšťalka" 🙂

The word "píšťalka" means "whistle" (and "pískat" is a verb "whistle"). If I try write it as it can be best said by english, it would be probably [peeshtialka] (try to read it as english word and you'll almost heard a czech word "píšťalka" :-). Both "a" is read as "u" in english word "up").
Ehm, exact translation is "little whistle" because "irská píštala" is already taken by another instrument - by "low whistle" (a "k" added into "píšťalka" makes it smaller).
Although a recorder is called "zobcová flétna" ("beak(?) flute") and whistle is very similar, it is not called "flétna". "Irská flétna" is "irish transverse flute" which is not a whistle :-). "flétna" itself is "transverse flute".

But if I say "píšťalka", many (non-music) people thinks that is something which uses football judge. Strange.

P.S.: Czech word for "tin" is "cín". And for "metal plate" it is "plech".

@ Kmarty
seems like flétna is the same as Flöte (floete) in german
that about the football judge is the same here too, its because of that little think with the pea inside the "trillerpfeife" (pfeife)

@Whistler
So if i say Whistle or even Whastles know native english speaker would think i play that thing with a little pea inside or am afootball judge?
Is Whastles just a form of pronaunciation or worth to be added into the "Tags" of the Blog articel? about the words for the instrument also called whistle

but would native speakers know that i mtalking about an instrument when i say whistle or would they think i am a football judge and play that pea inside thingy?